Taccalonolides: Mechanisms of Action and Cellular Resistance

描述（由申请人提供）：微管稳定剂是治疗癌症的宝贵药物。本项目的重点是一类新的植物来源的微管稳定剂，塔卡隆内酯。塔卡洛内酯对间期微管捆绑、有丝分裂纺锤体形态和有丝分裂信号通路有明显的影响。有效的新型他卡洛内酯已被首次鉴定，它们可以聚合纯化的微管，表明与微管蛋白/微管直接相互作用。微管蛋白聚合实验也表明，塔卡洛内酯与微管蛋白的相互作用方式不同于其他微管稳定剂。我们的初步数据表明，塔卡卡内酯结合在微管蛋白上的一个独特的位置。所有的他卡洛内酯都克服了临床相关的耐药机制，他卡洛内酯A和E对紫杉醇和阿霉素耐药小鼠乳腺癌模型具有体内抗肿瘤活性。研究人员建议对塔卡卡内酯的微管蛋白结合位点、这种结合的功能意义以及它如何阻断下游有丝分裂和间期信号传导进行全面的研究。这些研究有望发现一种新的微管蛋白结合位点或稳定微管的药效团。第一个目标是利用互补结构生物学方法确定塔卡卡内酯在微管蛋白/微管上的结合位点。第二个目标描述了他卡洛内酯与微管/微管在生物化学和细胞中的相互作用的功能意义。

DESCRIPTION (provided by applicant): Microtubule stabilizers are valuable drugs used in the treatment of cancer. The focus of this project is a new class of plant-derived microtubule stabilizers, the taccalonolides. The taccalonolides have distinct effects on interphase microtubule bundling, mitotic spindle morphology and mitotic signaling pathways. Potent new taccalonolides have been identified for the first time and they robustly polymerize purified tubuli indicating a direct interaction with tubulin/microtubules. The tubulin polymerization experiments also indicate that the taccalonolides interact with tubulin in a manner different from other microtubule stabilizers. Our preliminary data suggest that the taccalonolides bind within a unique site on tubulin. All of the taccalonolides overcome clinically relevant mechanisms of drug resistance and the taccalonolides A and E have in vivo antitumor activity against a paclitaxel and doxorubicin-resistant murine model of breast cancer. Comprehensive studies are proposed to identify the tubulin binding site of the taccalonolides, the functional significance of this bining and how this interrupts mitotic and interphase signaling downstream. These studies are expected to identify a new tubulin binding site or pharmacophore for stabilizing microtubules. The first aim will identify the binding site of the taccalonolides on tubulin/microtubules utilizin complementary structural biology approaches. The second aim describes the functional significance of the taccalonolide interaction with tubulin/microtubules biochemically and in cells. This aim will identify the effects of the potent taccalonolides on purified tubulin and on cellular microtubule dynamics. We anticipate that interruption of microtubule dynamics leads to mitotic signaling and interphase microtubule trafficking defects and ultimately cell death. The last aim will examine the structure-activity relationships of the taccalonolides to identify the specific chemical moieties necessary for optimal biological activities. Information gained from these studies will elucidate the chemical and biological properties of this new class of microtubule stabilizers. This is expected to lead to the identification of a new microtubule stabilizer binding site on tubulin that will provide new opportunities for rational drug development with the possibility of a unique spectrum of activity.